[CP] fix memory leak in host buffer reset. (flutter#55056)

Always resets host buffer, since each overlay context has its own host buffer

Author: Jonah Williams

shell/gpu/gpu_surface_metal_impeller.mm

@@ -187,13 +187,12 @@
  impeller::DlDispatcher impeller_dispatcher(cull_rect);
  display_list->Dispatch(impeller_dispatcher, sk_cull_rect);
  auto picture = impeller_dispatcher.EndRecordingAsPicture();
- const bool reset_host_buffer = surface_frame.submit_info().frame_boundary;
 
  return renderer->Render(
  std::move(surface),
- fml::MakeCopyable([aiks_context, picture = std::move(picture),
- reset_host_buffer](impeller::RenderTarget& render_target) -> bool {
- return aiks_context->Render(picture, render_target, reset_host_buffer);
+ fml::MakeCopyable([aiks_context, picture = std::move(picture)](
+  impeller::RenderTarget& render_target) -> bool {
+ return aiks_context->Render(picture, render_target, /*reset_host_buffer=*/true);
  }));
 #endif
  });

shell/gpu/gpu_surface_metal_impeller_unittests.mm

@@ -97,7 +97,7 @@ GPUCAMetalLayerHandle GetCAMetalLayer(const SkISize& frame_info) const override
  ASSERT_TRUE(frame->Submit());
 }
 
-TEST(GPUSurfaceMetalImpeller, ResetHostBufferBasedOnFrameBoundary) {
+TEST(GPUSurfaceMetalImpeller, DoesNotResetHostBufferBasedOnFrameBoundary) {
  auto delegate = std::make_shared<TestGPUSurfaceMetalDelegate>();
  delegate->SetDevice();
 
@@ -115,13 +115,13 @@ GPUCAMetalLayerHandle GetCAMetalLayer(const SkISize& frame_info) const override
  frame->set_submit_info({.frame_boundary = false});
 
  ASSERT_TRUE(frame->Submit());
- EXPECT_EQ(host_buffer.GetStateForTest().current_frame, 0u);
+ EXPECT_EQ(host_buffer.GetStateForTest().current_frame, 1u);
 
  frame = surface->AcquireFrame(SkISize::Make(100, 100));
  frame->set_submit_info({.frame_boundary = true});
 
  ASSERT_TRUE(frame->Submit());
- EXPECT_EQ(host_buffer.GetStateForTest().current_frame, 1u);
+ EXPECT_EQ(host_buffer.GetStateForTest().current_frame, 2u);
 }
 
 } // namespace testing